BY THE end, the place was overrun with Yankees fans and Yankees chants, and the Mets were left to slink back to their clubhouse with all of that venom echoing in their ears, with a haunting sense of foreboding lingering to their souls.

In their immediate past was another loss, this one 4-2 to the Yankees, this one given a humiliating exclamation point when Mariano Rivera drew a bases-loaded walk against Francisco Rodriguez to drive in an insurance run. The Yankees came into Citi Field and took no mercy on the bleeding Mets.

It’s simple, really: Starting tonight, against Milwaukee’s fence-bashers, the Mets begin a week that will define their season. And by this time next week, there is an excellent chance that all that water that Jerry Manuel has been talking about “treading” will instead be flooding their lungs, dropping them ever deeper into a puddle of irrelevance.

“We have to find a way,” the Mets’ manager said, “to figure this out.”

Maybe that inspiration came at 30,000 feet earlier this morning, somewhere on the team charter, between here and Milwaukee. Manuel had better hope so. The next seven days bring seven games in three cities, two of them home to two of the three clubs residing in first place in the National League — with the third first-place team, the Dodgers, awaiting them when they finally get back to Citi Field.

Assuming they get back here in one piece. Not an automatic assumption.

“We have our work cut out for us,” Manuel said softly. “There’s no question about that.”

The Phillies have backed out of their own way at last, winning by a blowout on Saturday and by their more traditional method yesterday, erasing a 4-1 lead in Toronto. By the time the Phillies take the field tomorrow in Atlanta — in a ballpark in which they went 9-for-9 last year — they will have Jimmy Rollins back after a four-day sabbatical that Charlie Manuel hopes will clear his head.

And they will know that the Mets will be looking for something, anything to hold on to in order to prevent their season from spiraling out of control.

They could have used better locations than Milwaukee, Pittsburgh and Philadelphia to locate those safety brakes, although after a 4-6 homestand maybe getting out of town isn’t the worst idea, either.

The Mets weren’t shut out this time. They exploded for a two-run outburst in the fourth inning, making Citi Field actually sound like a two-team ballyard for the first time all weekend, proving there is a pulse lurking beneath their jerseys.

And Livan Hernandez turned in another remarkable seven innings of work, muffling the Yankees on three hits, and he might even have been in line for a win if not for a top of the first inning that would have been comical if it wasn’t so . . . well, sad.

Poor Daniel Murphy. A year ago, he was threatening to become a genuine folk hero at old Shea Stadium. He showed up for work one day and started spraying line drives all over the place, and nobody much cared where he played on defense because, as these things happen, very few important balls ever seemed to go in his direction.

As opposed to the way things are now, when just about everything seems to find him.

This time, in a nightmarish first inning, he first made a horrific mental error by trying to nail Derek Jeter at third on a ground ball, then made a worse physical mistake by dropping the final leg of what would have been a pretty double play. Hernandez left the first inning trailing 3-0 when at worst it should have been 1-0.

These days, 3-0 might as well be 30-0. These days that now lead to a week through Milwaukee, Pittsburgh and Philadelphia with the Mets exactly at sea level, at 37-37.